Researches in Theoretical Geology |
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Common terms and phrases
abundant action amount appear aqueous argillaceous slates atmosphere basalt beds beneath bottom calcareous carbonate of lime carbonic acid cause chalk chemical chlorine circumstances coast consider considerable contorted cretaceous crust density deposits depths detected detrital matter detritus dislocations dry land earth earth's surface effects elevation entombed epoch equal exist exuviæ fathoms faults favourable felspar fissures force formed fossil fracture gaseous geological epochs Geological Manual globe gneiss granite grauwacke greater greenstone heat hornblende hydrogen igneous igneous rocks infer inferior stratified limestone lines liquid marine creatures mass mechanically suspended metallic mica mineral molluscs mountains observed ocean oolitic organic remains oxide oxygen particles percolation phænomena planet portion pressure probably produced quartz readily remarkable rivers sand sandstone Sandy mud shells silica similar situations slate species specific gravity strata stratified rocks substances sufficient suppose supracretaceous temperature terrestrial plants trachyte transported trappean valleys vapour various velocity volcanic volume
Popular passages
Page 388 - The other great accumulation of erratic blocks seems due to some more general cause, since not only are the blocks scattered in great abundance over northern Europe, in a manner to show their northern origin, but those which occur in the northern parts of America, apparently in equal abundance, also point to a similar origin. We hence infer that some cause situated in the polar regions has so acted as to produce this dispersion of solid matter over a certain portion of the earth's surface. We know...
Page 347 - ... are frequently not flattened, and altogether we have appearances which justify us in concluding that, since these organic exuviae were entombed they have been protected from the effects of pressure by the consolidation of the rock around them, and that they have been very tranquilly enveloped in exceedingly fine matter, such as we should consider would result from a chemical precipitate.
Page 330 - ... alternations up to the chalk. Many belong, however, to an entirely new race of plants from any which had previously existed. There are no longer the gigantic ferns and lycopodiums of the first period, — the same families exist, but the character of excessive luxuriance disappears, and species analogous to plants — now natives of the Cape of Good Hope and New Holland — become common. The whole of the...
Page 3 - ... probability, to be snow ; as they disappear when they have been long exposed to the sun, and are greatest when just emerging from the long night of their polar winter, the snow line then extending to about six degrees (reckoned on a meridian of the planet) from the pole.
Page 51 - ... six inches will lift fine sand ; eight inches, sand as coarse as linseed ; and twelve inches, fine gravel ; while it requires a velocity of twenty-four inches per second to roll along rounded pebbles an inch in diameter, and thirty-six inches per second to sweep angular stones of the size of a hen's egg.
Page 346 - Organic remains are in general beautifully preserved in the chalk ; substances of no greater solidity than common sponges retain their forms, delicate shells remain unbroken, fish even are frequently not flattened, and altogether we have appearances which justify us in concluding that, since these organic exuviae were entombed they have been protected from the effects...
Page 232 - ... atmospheres at another. A creature inhabiting a depth of 100 feet would sustain a pressure, including that of the atmosphere, of about...
Page 28 - Davy observed that oxygen and hydrogen gases unite slowly with one another, when they are exposed to a temperature above the boiling point of mercury, and below that at which glass begins to appear luminous in the dark. An explosive mixture diluted with air to too great a degree to explode by electricity, is made to unite silently by a succession of electric sparks. Spongy platinum causes them to unite slowly, though mixed with one hundred times their bulk of oxygen gas. A...
Page 386 - Alps outwards, on each side of this chain ; the other has proceeded from a northern direction southward. How far the events which have produced both accumulations of these blocks may have been separated by time from each other, we know not ; but we are certain that the geological epochs of both must have been very recent, since they both rest on rocks of little comparative antiquity.